This invention relates to filter apparatus and method for deep oil pressure cooking of successive batches of food and particularly to such oil filter apparatus and method to permit continuous use of the same oil.
A restaurant menu often includes chicken, fish and other foods which may be cooked or fried by immersion in hot cooking oil. Certain restaurants specialize in such foods, particularly deep cooked chicken. In addition to the conventional restaurant where the food is consumed on the premises, various restraurants and other food retail outlets have a substantial food carry-out business including chicken. In those restaurants and other outlets having large sales volume of cooked foods, a rapid and efficient cooker is essential in order to produce quality products at a reasonable and profitable cost.
The conventional apparatus for deep cooking includes a relatively large kettle or pot having a releasable high pressure sealed cover. The pot is filled with cooking oil to a level in spaced relation to the cover. A heating unit generally in the form of immersion heating elements or an encircling heat unit applied adjacent to the pot is operative to increase the temperature of the oil to the desired cooking level. As more fully disclosed in the inventor's copending application filed on even date herewith and entitled "Deep Oil Cooking Apparatus", the prior art pot structures and heating systems are costly and require substantial use of oil per pound of product cooked. The chicken is placed in a suitable basket for transfer and immersion into the cooking oil for deep cooking for a selected period and removable therefrom. For example, a widely used cooker includes a rectangular shaped pot of approximately 13-17 inches across and a similar depth. The cooker is adapted to maintain and cook approximately ten pounds of chicken parts in each cycle. The oil is raised to a temperature of 370.degree. to 375.degree. and the power may be cutoff just prior to placing the chicken in the pot or maintained. The chicken is then cooked for approximately eleven minutes and removed. Other commercial production units are constructed to operate with a continuous power supply and with the oil held at a temperature of at least 350.degree. F. to prevent boiling of the oil, while others suggest heating of the oil to even higher temperatures.
In all cookers, a system is provided for periodic withdrawal of the oil from the cooking apparatus and replacement with a new batch of fresh oil. Systems for filtering of foreign material from the oil which is created during the cooking process have also been suggested. The filter systems generally provide an open top container within which the oil is "dumped". The container has a suitable filter unit across the container to remove foreign product. Thus, a consistant and flavorable product is dependent upon use of clean oil which has not been burnt, oxidized or otherwise broken down. Although such systems are widely used, the present inventor has recognized a number of features which contribute to inefficiency of the cooking apparatus, as well as unnecessary costs in operation and oil usuage.
The oil is held at the high temperature and the temperature and air in the cooker above the oil level may cause scorching of the oil. The oil is contaminated with foreign matter during the cooking sequence and in general practice the oil is periodically replaced with a fresh batch of fresh oil, which may have been preheated. The replacement of the oil combined with the necessity of heating the oil reduces the efficiency of system operation.
Prior art commercial units have generally used immersion heating elements projecting into the oil within the lower end of the cooking pot and operated at temperature of at least 350.degree. Fahrenheit and in many instances at 375.degree. to 400.degree. Fahrenheit. The temperature at which oil will boil is approximately 360.degree. Fahrenheit and the immersion units are operated as close to such temperature as possible without significant possibility of boiling. However, because of the high temperature, some scorching of the oil results with a degradation of the oil. Further, at such high temperature significant oxidation of the oil may occur whenever the cooker is opened to replace the chicken. This is a particular problem because of the relatively large exposed surface area in the large shallow cooking pots. In addition, when cooking breaded products such as deep cooked chicken, some of the breaded coating, drops from the chicken during the cooking process. The crumbs and even small pieces of chicken fall through the oil to the bottom of the pot, and in so moving some is often deposited on the heating elements. The coating on the heating elements not only reduces the heat input into the oil but results in increased scorching of the oil as the result of the excessive frying of the breading product. Generally, the present day commercial apparatus requires frequent discarding of the oil and replacing of the oil with totally clean new oil.
The cooking oil is a significant cost factor of commercial production of deep cooked food and operators are continuously monitoring and taken such action as possible to minimize oil usage. This may result in using of oil which is marginally acceptable and compromising with a somewhat lesser quality product. This is particularly true in operations which may be operated by managers rather than owners of the commercial operation.
The cost of the oil in the prior art devices is particularly significant because of substantial quantities of oil used to cook products and the associated relatively high energy levels required to heat the oil. Generally, in commercial production 55 to 60 pounds of oil are used for batch cooking of 10 pounds of product. A large heating units operating to produce 11 to 12 kilowatts of energy are necessary to produce the proper temperature and time cycle. The heating units are distributed over the large surface of the oil to minimize the wattage per square inch of surface and thereby minimize scorching of the oil.
Although various deep cooking pot units are used in the industry, there is a continuing need for a more efficient and effective batch pressurized cooking pot-type apparatus and method having means to minimize the amount of cooking oil required to produce large volume of cooked product while maintaining an rapid and energy efficient cooking process.